Mycorrhiza in plant root cells
PHOTOGRAPH BY DE AGOSTINI PICTURE LIBRARY/GETTY

What's This Weird Fungus Growing On My Roots?

Answer: It's actually helping plants get the nutrients they need. Here's how it works.

June 30, 2015

Every time you walk into your garden, you’re stepping on a pipeline. It’s not a Jed Clampett–style oil pipeline, but it does have to do with a type of “black gold.” The pipeline I’m referring to is made up of hundreds and hundreds of miles of threadlike fungal hyphae, which are attached to the roots of plants. These slender, living strings of fungus retrieve nutrients and water from the soil and pump them directly to plant roots. Microorganisms, like insects, other fungi, and bacteria, break down fallen organic matter by consuming it, then excreting it in the form of nutrients: soil’s true black gold. After that, the fungi, called arbuscular mycorrhiza (arbuscular means “treelike”), act as a conduit to get the good stuff to the roots.

In exchange, plants supply the mycorrhizal fungi with sugars produced by photosynthesis. Fed by these sugars, the branching fungal network expands during the growing season. To keep it going, grow plants that will feed it after your harvest. Plant a temporary cover crop like annual ryegrass or clover, which will put down a new generation of roots to nurture the fungi through winter. And avoid tilling, which rips hyphae to pieces. Protect your garden’s pipeline year-round, and plants will be able to tap it and reap the benefits.

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Kris Nichols is the chief scientist at the Rodale Institute.

Tags: soil